In a telecommunications system, transmission to or from one or more mobile stations is achieved by means of a number of fixed stations each defining a cell, the cell being the area in which communication via the associated ground station can be effected.
In a mobile telecommunications system the mobile station, for example a mobile phone, normally comprises a logic circuitry which enables a fixed station to be selected and in a mobile phone application, for example, this selection could be made on the basis of signal strength.
The present invention is primarily concerned with a terrestrial flight telephone system, which systems are presently being deployed on commercial aircraft to enable telephone calls to be made on board the aircraft both whilst the aircraft is on the airport apron, and also whilst in flight. A detailed description of such a system is to be found in the European Telecommunications Standard Institute (ETSI) draft publication entitled: "Radio Equipment and Systems (RES) Terrestrial Flight Telephone System (TFTS) Part 2: Search Services, Radio Interface", dated July 1993 and subsequently updated and published as prETS300 326-2, the contents of which are hereby incorporated by way of reference. The ETSI document proposes a system in which a mobile air station selects a fixed ground station by a method summarised by the flow charts on pages 75-86 of that document. The method comprises establishing certain criteria relating to the mobile station, more particularly the aircraft on which it is located, and a number of fixed ground stations, and depending on those criteria an appropriate ground station is identified and a transmission effected via that ground station. This selection would for example be based on the closing rate alone to any ground station which had an acceptable signal strength.